1. Field of the Invention
The present invention relates to ergometer loading devices, and more particularly to an ergometer loading device with large braking force.
2. Description of the Background Art
An ergometer loading device of interest to the present invention is disclosed, for example, in Japanese Patent Publication No. 2-45905.
FIG. 6 is a block diagram which shows a main part of a bicycle ergometer disclosed in the publication. Referring to FIG. 6, the loading device of the bicycle ergometer includes a loading portion 50 to apply a load to a rider, and a control portion 60 to control loading portion 50. Loading portion 50 includes a load shaft 51 rotated when the rider presses down a pedal, a wheel 52 fixed on load shaft 51, and an annular disk 53 of a copper plate, for example, provided on the circumference of wheel 52. In order to facilitate rotation of disc 53, that is, wheel 52, an annular weight ring 54 having a flywheel function is attached to a linkage portion between wheel 52 and disk 53.
In connection with disk 53, only one electromagnet 57 is provided and fixed to a frame 58. Electromagnet 57 is formed of a core 55 and an exciting coil 56 which is wound around core 55 by means of a coil bobbin, not shown. Core 55, which is a C-shaped core having one opening, is provided to sandwich, in a non-contact manner, the both main surfaces of disk 53 between the opening end surfaces.
Exciting coil 56 has its one end terminal connected to a direct voltage source VD and its other terminal is connected to ground via a control transistor 61 and a resistor 62. The base of control transistor 61 is supplied with an output of a comparator 63. Control transistor 61, resistor 62, comparator 63, a CPU described below, and the like form control portion 60 and carry out a control operation so that a current, which is set, is supplied to exciting coil 56.
The setting of the current to be supplied to exciting coil 56 is controlled through a key board 66 provided for a control panel, not shown, CPU 65, a display 67 and a D/A conversion circuit 64 as described below. A user enters desired braking torque (a load of the ergometer according to the user""s athletic ability) by using key board 66. The entered braking torque is displayed on display 67 through CPU 65 and can be checked. When the braking torque is determined, CPU 65 calculates an exciting current which is necessary to add the braking torque.
Another example of the conventional ergometer loading device will be shown in FIG. 7. Referring to FIG. 7, the example of the conventional ergometer does not employ a C-shaped core as shown in FIG. 6 but it includes a drum shape in which a rotor rotates around a stator. Referring to FIG. 7, an inner circumferential rotor 72 of a structural carbon steel pipe (STK or STKM) is fit in an outer circumferential rotor 71 made of gray cast iron. On an inner stator 73, six exciting coils 74 are provided opposite rotor 72. Exciting coils 74 are connected in series with each other and have their both ends connected to a power supply 75 provided outside. In this case, the controlling and the like of the ergometer are the same as in FIG. 6.
The conventional ergometer loading device is formed as described above. In the example shown in FIG. 6, the opening (the portion denoted by A in FIG. 6) of C-shaped core 55 is about 1.7 mm, and disk 53 which is formed of a copper plate with a thickness of 1 mm is inserted in the opening. Since the attachment portion of core 55 and the attachment shaft of the copper plate are different, adjustment operations are difficult to avoid contact between the copper plate and core 55. Since the copper plate has a thickness of 1 mm, it is easily deformed by small external force, and it takes time to make an adjustment to avoid contact with core 55.
In the structure in which the copper plate is inserted in the C-shaped core, the total gap of an air gap and a thickness of the copper plate is proportional to magnetic resistance, and thus the magnetic resistance of the gap increases as the total gap becomes larger.
Since the loading device shown in FIG. 7 has a drum shape and coaxially includes a rotor corresponding to the disk and a stator forming the core, it does not cause the problems as in FIG. 6. However, the loading device uses carbon steel (at most 0.12%) for outer circumferential rotor 71 and inner circumferential rotor 72. In other words, the ferromagnetic body is also used for the conductor. Therefore, the generated braking torque is small.
Therefore, one object of the present invention is to provide an ergometer loading device which is adjusted easily and applies large braking force.
Another object of the present invention is to provide an ergometer loading device which is inexpensive, adjusted easily and applies large braking force.
Still another object of the present invention is to provide an ergometer loading device which is adjusted more easily and applies larger braking force.
An ergometer loading device according to the present invention includes a rotor which has a steel plate and a member of small electric resistance provided on the steel plate and is rotatable about a prescribed shaft, and a stator which is coaxial with the rotor and faces the rotor with a prescribed gap therebetween, the stator including a plurality of exciting coils, and a member of small electric resistance faces the stator with a prescribed gap therebetween.
According to the present invention, the stator is provided which is coaxial with the rotor and faces the rotor with a prescribed gap therebetween, and the member of small electric resistance faces the stator with a prescribed gap therebetween. Therefore, an ergometer loading device which is adjusted easily and applies large braking force can be provided.
Preferably, the member of small electric resistance is plated with copper.
More preferably, the thickness of the plated copper is from 0.01 mm to 0.8 mm.
In another aspect of the present invention, an ergometer loading device includes a rotor which has a steel plate and a member of small electric resistance provided on the steel plate, and a stator which faces the rotor with a prescribed gap therebetween. The stator includes a plurality of exciting coils, and the member of small electric resistance faces the stator with a prescribed gap therebetween.
In the aspect of the present invention, the member of small electric resistance provided on the rotor faces the stator with a prescribed gap therebetween, and thus an ergometer loading device which is adjusted easily and applies large braking force can be provided.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.